# From "Surely, You are Joking, Mr Feynman"

Feynman and Leighton, 1985

## Energy in Textbooks

("Judging Books by the Cover", p297-8) (Longer excerpt)

... For example, there was a book that started out with four pictures: first there was a wind-up toy; then there was an automobile; then there was a boy riding a bicycle; then there was something else. And underneath each picture, it said "What makes it go?"

I thought, I know what it is: They're going to talk about mechanics, how the springs work inside the toy; about chemistry, how the engine of an automobile works; and biology, about how the muscles work.

It was the kind of thing my father would have talked about: "What makes it go? Everything goes because the sun is shining." And then we would have fun discussing it:
"No, the toy goes becaues the spring is wound up, I would say.
"How did the spring get would up" he would ask.
"I wound it up"
"And how did you get moving?"
"From eating"
"And food grows only because the sun is shining. So it's because the sun is shining that all these things are moving" That would get the concept across that motion is simply the transformation of the sun's power.

I turned the page. The answer was, for the wind-up toy, "Energy makes it go." And for the boy on the bicycle, "Energy makes it go." For everything "Energy makes it go."

Now that doesn't mean anything. Suppose it's "Wakalixes." That's the general principle: "Wakalixes makes it go." There is no knowledge coming in. The child doesn't learn anything; it's just a word

What the should have done is to look at the wind-up toy, see that there are springs inside, learn about springs, learn about wheels, and never mind "energy". Later on, when the children know something about how the toy actually works, they can discuss the more general principles of energy.

It is also not even true that "energy makes it go", because if it stops, you could say, "energy makes it stop" just as well. What they're talking about is concentrated energy being transformed into more dilute forms, which is a very subtle aspect of energy. Energy is neither increased nor decreased in these examples; it's just changed from one form to another. And when the things stop, the energy is changed into heat, into general chaos.

This section is part of Richard Feynman's account of his work in a text-book committee, with many thoughts on teaching and learning and interpreting results ...
http://physics.gu.se/~f3aamp/teaching/wakalix.html